Control device for a fume extraction device

ABSTRACT

A fume extraction device including a fan for extracting fume-laden air from a cooking device in a room to an area located outside the room. The fume extraction device includes a pressure differential detection device for detecting the pressure difference (P d ) between an inside pressure (P i ) in the room and the outside pressure (P a ) in the area located outside the room. The fume extraction device further includes a control device for controlling the air conveying capacity of the fan according to the (P d ).

The present invention relates to a fume extraction device and a methodfor controlling a fume extraction device.

Fume extraction devices are preferably used in kitchens above a cookinghob in order to remove air laden with fumes and steam away from thecooking hob. In this case, a distinction is made between circulating-airhoods which extract air at the cooking hob, filter it and return it tothe room, and waste air hoods which extract the air, filter it andconvey it outside into the open.

If a waste-air hood is operated in a room with an open fireplace, thereis the risk that the waste gases produced at the fireplace will besucked into the room. In order to avoid this, numerous solutions havebeen proposed in the prior art.

DE 100 28 333 A1 discloses a safety radio circuit layout for a wasteair-fume extraction hood where the fume extraction hood is switched offwhen it is determined that an air inlet flap or another air inletopening such as a window or a door is closed. The transmission as towhether such an air inlet flap, a window or a door is closed isaccomplished by radio.

DE 30 40 051 A1 discloses a control device for awaste-air—circulating-air fume extraction hood wherein the waste air orthe circulating air is controlled depending on the pressure of the roomair.

JP 081 70 846 A discloses a fume extraction hood where a pressure sensoris provided in the waste-air channel. If the pressure of the waste airfalls below a pre-determined value, a control system deduces that awindow or a door of the kitchen is not opened, whereupon an air intakefan is set in motion to supply air into the kitchen so that an excessiveunderpressure is avoided in the kitchen.

JP 063 47 081 A discloses an air inlet and exhaust system comprising afume extraction hood where the inlet air is controlled by means of anair inlet throttle valve to avoid an underpressure in the kitchen.

DE 92 08 818 U1 discloses a fume extraction hood for a kitchencomprising a waste air channel and a circulating air channel which areinterconnected by means of a throttle. If the pressure in the kitchenfalls too steeply, waste air flows directly into the circulating airchannel via the throttle and thus back into the kitchen.

DE 910 10 95 U1 discloses a fume extraction device comprising a volumeflow rate measuring device which detects by means of the pressuredifference between the extraction connection and the environment of theextraction hood and determines therefrom the air volume flow ratethrough the extraction hood. The device monitors the air flow throughthe extraction and warns the user audibly and visually if the air volumeflow rate falls below or goes above air volume flow rate limits whichwould result in an unsafe operating state of the extraction hood.

DE 39 25 975 C2 discloses a switch-over device for selectivecirculating-air or waste-air operation of a fume extraction hood where aswitch-over unit is automatically actuated by means of a control devicewhich detects chimney-bound heating devices in the operating state sothat when a heater is operating, the fume extraction hood is switchedover to circulating air operation. The switch-over unit can be a drivenflap for example.

DE 17 81 986 U1 discloses an air flap for fans built into rooms whereoil furnaces are located where a room-ventilating flap is provided whichis opened to ventilate the room when the fan is started up.

These solutions described in the prior art are unsatisfactory becausethey are mostly too expensive.

It is the object of the present invention to provide a fume extractiondevice and a method for operating a fume extraction device whereinreliable operation of the fume extraction device in a room with an openfireplace is functionally safe and can be accomplished in a simplefashion.

This object is solved by the features of claims 1 or 2 or 12.

Since a control device which can be used in a fume extraction devicecomprising a fan, located in a room, comprises a pressure differencedetection device for detecting the pressure difference between theinside pressure in the room and the outside pressure in the area outsidethe room and a control device for recording the air conveying capacityof the fume extraction device depending on the detected pressuredifference, it is possible to reduce the air conveying volume if theunderpressure in the room becomes hazardous if an open fireplace isoperated in the room.

Measurement of the pressure difference between inside pressure in theroom and outside pressure in the area outside the room into which thefume extraction device conveys the waste air has the advantage that abalance between inside pressure in the room and outside pressure outsidethe room is always made independently of air pressure fluctuationsaccompanying changes in weather or independently of the height of theinstallation location. That is, the control device or the fumeextraction device provided with such a control device functions safelyand reliably at any installation location without the need to undertakeany calibration or subsequent adjustment.

In addition, this measuring device is very simple and thereforeinexpensive. In an advantageous embodiment of the invention, thepressure difference detection device has an inside pressure sensor andan outside pressure sensor and a comparator device to compare thedetected inside pressure and the detected outside pressure.

In an advantageous embodiment of the invention the pressure differencedetection device has a first sensor line which is connected to theinstallation room and a second sensor line which is connected to thearea outside the room.

In an advantageous embodiment of the invention the pressure differencedetection device is preferably arranged in the room at the fumeextraction device or in the area outside the room or partly in the roomand partly in the area outside the room.

A very simple detection between inside pressure and outside pressure inthe area outside the room can be made using the arrangementshereinbefore.

In an advantageous embodiment, the pressure difference detection devicecomprises a membrane which is connected on one side by means of a firstsensor line to the room and is connected on the other side by means of asecond sensor line to the area outside the room. The membrane is thusacted upon by the pressure in the room on one side and by the pressureoutside the room on the other side. This arrangement is especiallysimple and inexpensive especially if the first and/or the second sensorline is constructed as a hose line.

In an advantageous embodiment a duct is provided for guiding thefume-laden air into the area outside the room and the second sensor lineis laid along or in the duct in the area outside the room. It is therebypossible to use for the second sensor line an already existing wallopening or an already existing duct for laying the sensor line.

In an advantageous embodiment the control device controls the fan suchthat, preferably in a control loop, the inside pressure with respect tothe outside pressure does not fall below a pre-determined pressuredifference threshold of preferably 4 Pascal or that the fan is switchedoff if the inside pressure with respect to the outside pressure fallsbelow a pre-determined pressure difference threshold of preferably 4Pascal and that the fan is switched on if the inside pressure withrespect to the outside pressure increases above the pre-determinedpressure difference threshold.

In an advantageous embodiment of the invention a warning signal issuingdevice is provided which issues a warning signal if the inside pressurefalls below a pressure difference threshold of preferably 4 Pascal.

The output warning signal can be an audible warning signal preferably inthe form of an interrupted warning tone and/or a visual signalpreferably in the form of a flashing red light and/or in the form of adisplay which indicates to the user “open window” or “ventilate room”.

Further features and advantages of the invention are obtained from thefollowing description of the exemplary embodiment with reference to theappended drawing.

FIG. 1 shows a waste-air fume extraction device in a room.

According to the figure, the fume extraction device 1 has a housing 2, afan 3 and a control device 4. The fume extraction device 1 is located ina room 5 with the inside pressure P_(i) above a cooking hob 6. The fumeextraction device 1 conveys air laden with fumes and vapours via a duct7 through a wall opening 8 into an area 9 outside the room 5 with anoutside pressure P_(a).

The control device 4 has a pressure difference detection device 10, acontrol device 11 for controlling the fan 3 depending on the pressuredifference between the inside pressure P_(i) and the outside pressureP_(a) detected by the pressure difference detection device 10.Furthermore, the control device has a warning signal issuing device 12which can emit a warning signal at a pre-determined pressure differencethreshold between the inside pressure P_(i) and the outside pressureP_(a).

The pressure difference detection device 10 has a pressure sensor,preferably embodied as a membrane which is connected on one side via afirst sensor line 14 to the room 5 and is thus acted upon by the insidepressure P_(i) and on the other side is connected via the second sensorline 15 to the area 9 outside the room 5 and is acted upon by theoutside pressure P_(a). The first and the second sensor line 14 and 15are constructed as flexible hose lines.

The pressure difference detection device 10 is able to detect thepressure difference between the room 5 which is at the pressure P_(i)and the pressure in the area outside the room 5 which is at the pressureP_(a) by means of the first sensor line 14 and the second sensor line15. Since a fume extraction device extracts a large amount of air fromthe room 5, an underpressure is formed in this room 5 which has theresult that the extracted air from the room 5 must flow back into theroom 5 via gaps at doors and windows. If an open fireplace with achimney is located in the room 5, there is a risk that smoke and exhaustgases from the open fireplace will be sucked back into the room 5 viathe chimney as a result of the underpressure formed in the room 5.Experience has shown that there is a serious risk if the inside pressureP_(i) in the room is 4 Pascal lower than the outside pressure P_(a) inthe area 9 outside the room 5 into which the fume extraction deviceconveys the waste air.

If the control device 4 receives the message from the pressuredifference detection device 10 that the underpressure in the room 5 hasfallen below the pressure difference threshold of 4 Pascal, the controldevice switches off the fan and issues a warning signal via the warningsignal issuing device 12 so that a user, for example, a cook, opens aroom ventilation device such as, for example, a window or a door. If thepressure difference detection device 10 detects that the underpressurein the room 5 has fallen below the pressure difference threshold of 4Pascal again, the control device 4 switches the fan 3 on again.Alternatively to switching off the fan when the pressure differencethreshold of 4 Pascal is exceeded, the control device 4 can regulate thespeed and therefore the quantity of air conveyed by the fan 3 so thatthe pressure difference threshold of 4 Pascal is not exceeded. In thisway a certain amount of extraction, a so-called emergency operation ofthe fume extraction device can be maintained wherein the required safetyis ensured at the same time.

A buzzer can be provided as a warning signal issuing device 12 whichissues a warning tone, preferably an interrupted warning tone or avisual signal such as a flashing red light and/or a display whichilluminates an instruction such as, for example, “ventilate room” or“open window” or the like.

The control device 4 which comprises the pressure difference detectiondevice 10 and the control device 11 can be fitted as a unit in alreadyexisting fume extraction hood, in which case it is only necessary to laya second sensor line 15 in the form of a hose through the duct 7 in thearea 9 outside the room 5 and provide a corresponding electricalconnection between the fan 3 and the control device 4.

Instead of the previously described membrane, the pressure differencedetection device 10 for detecting the pressure difference P_(d) betweenthe inside pressure P_(i) in the room 5 and the outside pressure in thearea 9 outside the room 5 can comprise an inside pressure sensor (notshown) and an outside pressure sensor (not shown) and a comparatordevice for comparing the detected inside pressure and the detectedoutside pressure.

1-15. (canceled)
 16. A control device for use in a waste-air fumeextraction device, comprising: a room; a cooking device in said room; afan arranged in said room; a pressure difference detection device fordetecting the pressure difference (P_(d)) between the inside pressure(P_(i)) in said room and the outside pressure (P_(a)) in the areaoutside said room; and a control device for controlling the airconveying capacity of the fume extraction device depending on thedetected pressure difference (P_(d)).
 17. A fume extraction device,comprising: a fan for extracting the fume-laden air from a roomcontaining a cooking device and conveying the extracted air to an areaoutside said room; a pressure difference detection device for detectingthe pressure difference (P_(d)) between the inside pressure (P_(i)) insaid room and the outside pressure (P_(a)) in said area outside saidroom; and a control device for controlling the air conveying capacity ofsaid fan depending on the detected pressure difference (P_(d)).
 18. Thedevice according to claim 17, including said pressure differencedetection device having an inside pressure sensor and an outsidepressure sensor and a comparator device for comparing the detectedinside pressure and the detected outside pressure.
 19. The deviceaccording to claim 17, including said pressure difference detectiondevice connected to said room via a first sensor line and connected tosaid area outside said room by means of a second sensor line.
 20. Thedevice according to claim 17, including said pressure differencedetection device arranged in at least one of said room at the fumeextraction device, said area outside said room or partly in said roomand partly in said area outside said room.
 21. The device according toclaim 17, including said pressure difference detection device includes amembrane which is connected on one side by means of a first sensor lineto said room and is connected on the other side by means of a secondsensor line to said area outside said room.
 22. The device according toclaim 21, including at least one of said first and said second sensorline is a hose line.
 23. The device according to claim 21, including aduct provided for guiding the fume-laden air into said area outside saidroom and said second sensor line is laid at least one of along or insaid duct from said room into said area outside said room.
 24. Thedevice according to claim 17, including said control device controlssaid fan such that at least one of said inside pressure (P_(i)) withrespect to the outside pressure (P_(a)) does not fall below apre-determined pressure difference threshold (P_(d)) of preferablysubstantially about 4 Pascal, said fan is switched off if said insidepressure (P_(i)) with respect to said outside pressure (P_(a)) fallsbelow a pre-determined pressure difference threshold (P_(d)) ofpreferably substantially about 4 Pascal and that said fan is switched onif said inside pressure (P_(i)) with respect to said outside pressure(P_(a)) increases above a pre-determined pressure difference threshold(P_(d)).
 25. The device according to claim 24, including said controldevice controls said fan in a control loop.
 26. The device accordingclaim 17, including a warning signal issuing device is provided whichissues a warning signal if said inside pressure falls below a pressuredifference threshold (P_(d)) of preferably substantially about 4 Pascal.27. The device according to claim 26, including said output warningsignal is at least one of an audible warning signal preferably in theform of an interrupted warning tone, and a visual signal preferably inthe form of a flashing red light and a visual signal in the form of adisplay “open window” or a display “ventilate room”.
 28. A method foroperating a fume extraction device including a fan for extracting thefume-laden air from a room containing a cooking device and conveying theextracted air to an area outside the room, comprising: detecting thepressure difference (P_(d)) between the inside pressure (P_(i)) in theroom and outside pressure (P_(a)) in the area outside said room; andcontrolling the air conveying capacity of the fan depending on saiddetected pressure difference (P_(d)).
 29. The method according to claim28, including controlling said conveying capacity of said fan such thatsaid inside pressure (P_(i)) with respect to said outside pressure(P_(a)) does not fall below a pre-determined pressure differencethreshold (P_(d)) of preferably substantially about 4 Pascal.
 30. Themethod according to claim 29, including switching off said fan if saidinside pressure (P_(i)) with respect to said outside pressure (P_(a))falls below a pre-determined pressure difference threshold (P_(d)) ofpreferably substantially about 4 Pascal and switching off said fan ifsaid inside pressure (P_(i)) with respect to said outside pressure(P_(a)) is above said pre-determined pressure difference threshold(P_(d)).
 31. The method according to claim 28, including issuing awarning signal if said inside pressure (P_(i)) with respect to saidoutside pressure (P_(a)) falls below a pre-determined pressuredifference threshold (P_(d)) of preferably substantially about 4 Pascaland switching off said warning signal if said inside pressure (P_(i))with respect to said outside pressure (P_(a)) increases above saidpre-determined pressure difference threshold (P_(d)).